Issue

The Occam Process: A Package-first Approach to Electronics Assembly

09/01/2007

The Occam Process: A Package-first Approach to Electronics Assembly

Tin-lead solder was pressed into service as means of making reliable permanent interconnections between electronic elements in the early years of the electronics industry. While solder technology has been a vital part of the electronic interconnection assembly process ever since, it is not without limitations. Those limitations have been stressed near to the breaking point by the European Union (EU) Parliament’s decision to ban the use of lead in electronic solder with its RoHS legislation. The lead-free era has created problems for the electronics industry requiring development of materials, processes, and equipment to meet the challenges posed by lead-free soldering. While great effort has been put into making these products reliable and cost competitive, the alloys are more expensive and require increased time and energy to process, when moisture bakes and reflow oven temperatures are included. In addition, the ultimate reliability of lead-free is still not completely known as the number of different finishes, solders, fluxes, and process variations create a matrix of immense proportions. In effect, the entire electronics industry is now bending and bowing to the dictates of a small family of often-proprietary tin-metal alloys as solder has risen from being a servant of electronics to become its not-so-benign dictator; forcing its will upon all of the other constituent elements of electronics assemblies from components to PCBs.

Faced with such an intractable problem and anticipating that the challenges ahead for electronics assembly are not going to get any easier, a way to assemble electronics in a new manner has been conceived. The latest method reverses the order of standard assembly. In simplest terms, the components are first placed on a planar carrier in predetermined positions - as if for mounting on a PCB - and then encapsulated. The encapsulated component carrier is flipped over and the components terminations are cleaned to assure good electrical interconnection. Circuits are then produced layer by layer on top of the carrier using any of a number of different processes, from well-understood and accepted build-up circuit processing, to discrete wire connections using resistance welding, or any of the developing direct-write technologies on the horizon.

The new technology is called the Occam Process, in honor of 14th-century English philosopher and logician William of Occam, who noted that simplicity is the ultimate test of a conclusion or explanation. In short, the simplest solution is likely to be the best. The new process has many advantages, and does away with all but the most fundamental elements needed for an electronic assembly, which include reliable (e.g., tested and burned-in) components, a mechanical support for holding them together, and interconnections between component terminals. Although nothing else is needed for the product, there will be some concerns with the new process.

We are accustomed to believing electronics assembly requires certain materials, process steps, and checks, but are they really necessary? Electrical testing, for example, is very important in today’s manufacturing environment because the results of assembly are never certain. There are simply too many factors to consider, all of which are subject to change and variability, which is often the result of the process itself. Shorts, opens, component value changes, damaged components, and the like can all be found by testing; but what causes them? High temperatures of most lead-free solders are pushing component reliability to its limits.

This begs the question: how many of the faults uncovered by testing are the result of processes and materials that have been pushed beyond their reliability thresholds? If a highly reliable and benign process was developed that resulted in every product turning on the first time, would testing still be required? This same exercise can, and arguably should, be performed for all areas of manufacturing and assembly. We need to continually test our assumptions to make certain that we are making informed and well-considered decisions.

In summary, the electronics manufacturing industry is at a crossroad. It will be choosing a path forward because it cannot stand still. The ability to change and adapt has long been a key part of the makeup of the electronics industry but change is often painful and normally slow. The Occam Process is intuitively simple, it bypasses the complex problems and challenges of lead-free solder, and will provide highly reliable products at low cost with minimal energy use and waste. Whether these advantages are sufficiently persuasive for the electronics industry to adapt to this type of change remains to be seen. But given the present circumstances and the positive response the concept has enjoyed thus far, the prospects look favorable.